Process for making ethereal esters from aliphatic aldehyde esters and aliphatic alcohols



Patented Aug. 1 1 1953 UNITED STATES ATENT OFFICE PROCESS FOR MAKING ETHEREAL ESTERS FROM ALIPHATIC ALDEHY DE ESTERS AND ALIPHATIC ALCOHOLS No Drawing. Application May 18, 1951, Serial No. 227,099

Claims.

This invention relates to a novel process for the preparation of high molecular weight aliphatic ethereal esters. More particularly, it relates to a novel process of preparing ethereal esters having from 12 to 60 carbon atoms.

This application is a continuation-in-part of Serial No. 61,913, filed November 24, 1948, now Patent No. 2,578,724.

The method of this invention comprises heating a mixture of an aliphatic aldehyde ester and an aliphatic alcohol and removing the water formed by the condensation as it is produced, and thereafter isolating the ethereal esters. Acid catalysts such as mineral acids, toluene sulfonic acid, mercaptans, etc., may be used if desired, since they seem to promote the reactions, but they are not absolutely necessary for obtaining satisfactory yields of the desired unsaturated esters. The resulting ethereal esters are unsaturated and can be hydrogenated to produce the saturated esters.

The reactions involved are illustrated by Equations I through III below, beginning with the formation of the unsaturated ester, and wherein R, R. and R" are alkyl groups which can be the same or different, at is an integer of from 2 to 10, and the total carbon atom number is from 12 to 60:

Esterification RCH=CH(CH)COOH ROH R-CH=CH(CH2)=COOR HOH Equation I Oxomttion to aldehyde ester RCHCH(CHz)eCO0R I (Mixture of isomers) thesis, etc. 1948, and 70 JACS 383 (1948)). The alcohols utilized in the esters of Equation I and the etherification reaction of Equation III can also conveniently be prepared by the same process. The term 0x0 process is well understood in the art as referring to a process wherein an olefinic feed is first reacted or oxonated with carbon monoxide and hydrogen at a temperature between 120 and 250 C., and under a pressure of about 150 to 400 atmospheres in the presence of a cobalt or similar catalyst, generally introduced in the form of a fatty acid salt, to form aldehydes in accordance with the following reaction:

The most readily available olefinic feed stocks for the 0x0 reaction as outlined above are selected hydrocarbon streams derived from petroleum refinery sources.

The alcohols formed by oxonation of the olefinic materials described above are naturally quite complex in character and the exact composition of many of these products is not known.

The Ca branched chain primary 0x0 alcohols obtained have thus been found to comprise a mixture of isomers.

The entire process to yield the unsaturated ethers is quite simple and economical in operation. The alcohol and aldehyde esters, which can have either the same or different R, R and R." carbon skeleton structures and are preferably of the more desirable branched chain carbon structures, are heated together under heating conditions such as might ordinarily be employed for an esterification in theliquid phase at a temperature in the range of about 90 C. to 275 C. The temperature must be adjusted CH0 properly such that the unsaturated ether may be formed at a sufiiciently great reaction rate as Equatmn H to make the operation of a practical nature. Un-

reacted starting materials and certain lower Etherifica io boiling by-products can be removed from the HO--R Equation III system by distillation, since normally the unsaturated ethereal esters will be the highest boiling material present in any substantial amount. This affords a convenient method for isolation of the product. Unreacted aldehyde ester and alcohol can be removed by volatilization fromthe reaction mixture and can, of course, be subjected to the reaction again to increase conversion to the unsaturated ether. Th most practical procedure is to carry out at least the latter part of the distillation under reduced pressure to reduce product decomposition and tar formation. The quantity of water which is produced during the initial stages of the reaction period prior to distillation of the product and is removed as formed can be used as a convenient indication of the extent of completion of the reaction. If it is desired to remove the unsaturated ethereal esters product from the reaction mixture by distillation, this should be done at reduced pressures to avoid decomposition.

It is not known just what kind of condensations occur in the reaction mixture or just whatintermediates may be formed preceding the formation of the ether product. In fact, several mechanisms are very likely occurring simultaneously during the reaction.

It is not intended to in any way limit the process of the invention to any particular mech-' anism or mode of reaction.

The molar ratios of the reactants are not critical and various mixtures of aldehyde esters and alcohols may be conveniently employed. Any reasonable excess of either aldehyde ester or alcohol is readily recycled. A moderate excess of alcohol appears to favor the reaction. For instance, the aldehyde ester to alcohol mole ratio may be advantageously held at about 1:3.

Since water is a lay-product, the reaction is facilitated by: removal of water and gives increased unsaturated ether formation. This water removal may be conveniently handled by addition of an entrainer such as benzene, toluene; or the xylenes or excess alcohol. The water is thus removed as one'component of an azeotrope, the components of the azeotrope are separated, and the entrainer subsequently recycled.

The aldehyde esters and alcohols which may be converted tothe unsaturated ethers by this improved technique include any of those of the aliphatic series. For best yields of the unsaturated ethereal esters it has been discovered that the more highly branched aldehydes and alcohols are much to be preferred. The reactants may be substituted by non-reactive substituents such as halogen atoms. Use of unlike aldehyde and alcohol compounds will result in unsymmetrical ethereal esters. Under these circumstances; mixtures or mixed esters will be obtained.

The reactants employed need not be chemicall y pure components and the process can be operated with mixtures. The process is especially useful on synthetic mixtures such as can be roduced by reacting various higher olefins with carbon monoxide and hydrogen, a reaction commonly known as the x0 reaction. Aldehyde esters and alcohols from other types of synthetic sources may also be used. The present process ofier a very advantageous method for converting crude distilled fractions which contain both higher alcoholsand aldehyde esters such as those having 6 to 30 carbon atoms to highly useful and relatively easily isolatable product. Thisuse of crude. mixtures of. reactants is, in fact, one ofthe outstanding, advantages of this novel process.- The process is also one of great simplicity bothin-the operational procedure and in the apparatus necessary.

The unsaturated ethereal esters are identified in the usual way by determination of the bromine number, molecular weights and elemental analyses. Infrared analyses show the characteristic olefinic band as well as the ether band. Comparison. ofthe elemental analysis with the calculated values gives an additional check on the structure-or the compounds formed.

It is a further great advantage of this process, that no intermediate products need be isolated. This results in an increase in yield of the desired product and ofiers a great many operational advantages. Thus a great deal of equipment and labor is eliminated in addition to a great time saving in starting with the original raw materials and obtaining the final product.

The unsaturated ethereal esters can be hydrogenated in conventional manners to produce the saturated esters, utilizing catalysts such as nickel-kieselguhr, copper chromite or sulfur acti-ve catalysts.

This invention is illustrated by the following examples:

Example I .-Unsaturu.ted ethereal ester Iso-octyl oleate was prepared by refluxing 570.8 gins. of oleic acid with 520.0 gins. of isooctyl alcohol, 300 cc. of benzene and 5 drops of 70% sulfuric acid. The mixture was treated under entrai ment conditions at 24 0 250f F; for 3 hours, during which time a'total of 3815 cc. of"

GSO-gms. of the oxo product (equivalent to 0.92 mole of aldehyde) were mixed with 431 gms. of iso-octyl alcohol, 300 cc. of benzene, and 2- cc. of 50% sulfuric acid and the mixture was allowed to stand for 2 weeks. The mixture was then heated under entrainment conditions for 4 hours during. which time 16 cc. (0.89 mole) of water were removed.

The product was distilled to remove benzene and unreacted: iso-octyl alcohol.

Cut #1, 165'-200 17.16 Wt. percent (benzene) Cut #2, 200-378 F., 23.76 Wt. percent (iso-oct'yl alcohol) Bottoms, 378 F.+, 59.08 Wt. percent (unsaturated ethereal ester) The bottoms from this distillation was examined by infrared-and-showed sharp bands corresponding to the 0:0 and C-OC' linkages.

Example ZIP-Saturated ethereal ester A sample of bottoms from Example I was hydrogenated over U. 0-. P. nickel catalyst (18% catalyst at 350 F.) the product filtered and then vacuum stripped to remove a small quantity of C3 alcohol. The final product showed the following inspections.

Ester No. 117:

Theoretical for ethereal ester=104 Theoretical for iso-octyl' oleate=142 thus purit'y' as ethereal ester.

Hydroxyl N0; 21: Theoretical for ester alcohol-'-"131 =5 21 /l31.5=1-6-%'alcohol;

The unsaturated ethereal esters have utility as plasticizers, synethetic lubricants, specialty solvents and chemical intermediates.

The saturated ethereal esters also have utility as plasticizers, synthetic lubricants, solvents and chemical intermediates.

It will be understood further that the foregoing examples have been given merely for purposes of illustration, but that other modifications of the present invention are possible without departing from the scope of the appended claims.

What is claimed is:

1. A process for the preparation of an unsaturated aliphatic ethereal ester having the general formula which comprises heating a, mixture of a saturated 6 aliphatic aldehyde ester corresponding to the general formula with an aliphatic alcohol corresponding to the formula R"OH wherein R, R and R" are alkyl groups which can be the same or different, a: is an integer of from 2 to 10, and the total carbon atom number of the aliphatic ethereal ester is from 12 to 60, removing the water so formed as it is produced, and thereafter isolating the unsaturated ethereal ester.

2. The process of claim 1 in which the alcohol is a branched chain alcohol.

3. The process of claim 2 in which the branched chain alcohol is obtained by the OX0 process.

4. The process of claim 1, including the additional step of hydrogenating the unsaturated ethereal ester product to obtain a saturated ethereal ester.

5. A process for the preparation of an aliphatic unsaturated ethereal ester, which comprises heating a saturated aliphatic aldehyde oleic acid ester of a Cs branched chain aliphatic alcohol prepared by the OX0 process with additional Ca branched aliphatic alcohol prepared by the 0x0 process, removing the water formed as it is produced, and thereafter isolating the ethereal ester product.

JOSEPH K. MERTZWEIILER.

References Cited in the file of this patent Geiges: Abstract of Application SLN. 466,487, published August 9, 1949. 

1. A PROCESS FOR THE PREPARATION OF AN UNSATURATED ALIPHATIC ETHEREAL ESTER HAVING THE GENERAL FORMULA 